Supersensitized silver halide photographic emulsions

ABSTRACT

A green-sensitive silver halide photographic emulsion for color photographic materials super-sensitized by a combination of a specific benzimidazolo oxacarbocyanine dye and a specific oxacarbocyanine dye.

United States Patent Shiba et al.

[ 1 Dec. 17, 1974 SUPERSENSITIZED SILVER HALIDE PHOTOGRAPHIC EMULSIONS Inventors: Keisuke Shiba; Masanao l-linata;

Akira Sato; Akira Ogawa; Tadashi Ikeda, all of Kanagawa, Japan Fuji Photo Film Co., Ltd., Kanagawa, Japan Filed: Jan. 5, 1973 Appl. No.: 321,423

Assignee:

[56] References Cited UNITED STATES PATENTS 3,397,060 8/1968 Schwan et a1 96/124 3,580,724 5/1971 Sato et a1 i i t 96/124 3,663,210 5/1972 Sato et a1. 96/124 Primary Examiner.1. Travis Brown Attorney, Agent, or FirmSughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT A green-sensitive silver halide photographic emulsion for color photographic materials super-sensitized by a combination of a specific benzimidazolo oxacarbocyanine dye and a specific oxacarbocyanine dye.

17 Claims, No Drawings SUPERSENSITIZED SILVER HALIDE PHOTOGRAPHIC EMULSIONS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a spectrally sensitized silver halide photographic emulsion and particularly to a silver halide photographic emulsion supersensitized by a combination of two kinds of sensitizing dyes. More particularly, the invention relates to a supersensitized green-sensitive silver halide photographic emulsion for color photographic materials.

2. Description of the Prior Art Spectral sensitizing techniques or techniques of extending the sensitive wave length region of a silver halide photographic emulsion to the longer wave length side by incorporating a certain cyanine dye in a silver halide photographic emulsion are well known in manufacturing photographic light-sensitive materials.

The spectral sensitization depends upon the chemical structure of the sensitizing dye and various properties of the silver halide emulsion employed, such as the halogen composition, the crystal habit, the crystal system, the silver ion concentration, and the hydrogen ion concentration of the silver halide emulsion. The spectral sensitization is further influenced by photographic additives incorporated in the photographic emulsion, such as a stabilizer, an antifoggant, a wetting agent, a precipitant, a color coupler, etc.

In order to sensitize a definite spectral wave length region of a photographic light-sensitive material, only one kind of sensitizing dye may be used, but in many cases a combination of two or more kinds of sensitizing dyes is used. In the case of employing such a combination of sensitizing dyes, however, it frequently happens that the spectral sensitivity obtained is lower than the sensitivity obtained with the separate use of each of the sensitizing dyes. However, in certain specific cases the spectral sensitivity obtained by such a combination of sensitizing dyes is in an increased super additive manner by employing a combination of a specific sensitizing dye and one or more other specific sensitizing dyes. This phenomenon is known as supersensitization. In such a supersensitization, even if the difference of chemical structure between one sensitizing dye and the other sensitizing dye is slight, the difference in the supersensitizing action between them is frequently quite large. Accordingly, it is known that a combination of sensitizing dyes showing a supersensitizing action can hardly be predicted from the chemical structures thereof alone.

Therefore, in manufacturing photographic emulsions the sensitizing dyes to be used as a combination thereof for supersensitization must be quite carefully selected. The sensitizing dyes used in the case of applying supersensitization to a silver halide photographic emulsion must also have no harmful co-action with other photographic additives and must have stable photographic properties even during the preservation of photographic light-sensitive materials which contain such dyes.

Some photographic additives, when added to a silver halide photographic emulsion, decrease the spectral sensitivity thereof, and examples of such additives are anionic compounds such as light-absorbing dyes having an anionic group, e.g., a sulfo group; gelatin precipitants having an anionic group, e.g., a sulfo group or carboxyl group; and couplers for color photographic materials. In particular, in the case of a green sensitive silver halide photographic emulsion for color photographic light-sensitive materials, the change of spectral sensitivity when a supersensitizing combination of dyes is present with a magenta coupler in the emulsion is important.

Sensitizing dyes are further required to leave no color stain in the photographic light-sensitive materials after development. In general, a sensitizing dye leaves color stains in the image-bearing emulsion layers and/or subsidiary layers (intermediate layers, etc.,) or on the developed and fixed support. Such an harmful influence due to remaining dyes must be corrected by photographic means used in the photo-engraving process, such as a color masking method, and such a color correction is particularly troublesome in the case of a lithographic photographic negative which must have a light grey color. This effect of the remaining dyes is also undesirable in photographic papers since in the case of black and white photographic papers a bright white color is not obtained, and in the case of color photographic papers true color reproduction becomes impossible.

Further, if a yellow or magenta color (or a yellow or magenta dye) dye remains other difficulties occur, e.g., when a part of a finished photograph is exposed to sun light the dyes at that portion are bleached by the sun light, which results in a partially bleached and partially colored image. Consequently, in the case of sensitizing photographic emulsions using sensitizing dyes, it is important to prevent the sensitizing dyes from remaining in the finished photographic paper, lithographic film, or other photographic film or plate.

Moreover, the sensitizing dyes used are also required to give a spectrally sensitive region sufficiently stable to a safe light which is used in processing light-sensitive materials. For color photographic light-sensitive materials, in particular color positive films or color papers, a safe light having a maximum percent transmission at about 570-620 mu is generally used. Therefore, the long wave length side of the spectrally sensitive region of a green-sensitive emulsion layer thus sensitized has usually been sharply cut so that the emulsion layer is stable under the safe light. If this is not done, fog is formed by the action of the safe light to cause stains on the finished photograph.

SUMMARY OF THE INVENTION One object of the present invention is to provide a silver halide photographic emulsion supersensitized by a combination of sensitizing dyes which leave less residual dyes or colors in the finished photographic product.

Another object of this invention is to provide a silver halide photographic emulsion supersensitized by a combination of sensitizing dyes, the spectral sensitivity of which is not reduced during the storage of the silver halide emulsion thus sensitized, as well as during storage of photographic light-sensitive materials having layers of the silver halide emulsions thus sensitized, even when the silver halide emulsion or emulsion layer further contains compounds with one or more anionic group(s), such as a gelatin precipitant (as set forth in US. Pat. Nos. 3,138,461, 3,241,969, 3,366,482, 3,455,694, 3,522,053, British Pat. No. 1,103,420, German Pat. No. 1,238,370, etc.), an anionic activating agent (as set forth in U.S. Pat. Nos. 3,003,877, 3,026,202, 3,201,252, 3,415,649, etc.) or a color coupler such as a magenta coupler (refer, for example, to P. Glafkidis Photographic Chemistry, vol. II pp. 5966l5).

DETAILED EXPLANATION OF THE INVENTION The above and other objects of this invention are attained by using the combination of selected benzimidazolo.oxacarbocyanine dyes and selected oxacarbocyanine dyes. The combination of such dyes provides a valuable technical advance in the production of wherein A, and A each represents a hydrogen atom, a halogen atom (e.g., a chlorine atom, a bromine atom, a fluorine atom, an iodine atom), a hydroxyl group, an alkoxyl group (e.g., a methoxy group, an ethoxy group), an amino group or an alkyl-substituted amino group such as (e.g., an amino group, a methylamino group, a dimethylamino group), an acylamide group (e.g., an acetamido group), an acyloxyl group (e.g., an acetoxyl group), a carboalkoxyl group (e.g., a carboethoxy group), an alkoxycarbonylamino group (e.g., an ethoxycarbonylamino group), a cyano group, a trifluoromethyl group, an alkoxycarbonyl group (e.g., a methoxycarbonyl group, an ethoxycarbonyl group), an alkyl su lfonyl group (e.g., a methylsulfonyl group), a

up to 6 carbon atoms or a substituted alkyl group as is conventionally used as an N-substituent of a sensitizing cyanine dye (e.g., a methyl group, an ethyl group, an n-propyl group, a vinyl methyl group), a hydroxyalkyl group (e.g., a 2-hydroxyethyl group, 4-hydroxybutyl group), an acetoxyalkyl group (e.g., a Z-acetoxyethyl group, a 3-acetoxypropyl group), an alkoxyalkyl group (e.g., a 2-methoxyethyl group, a 4-butoxybutyl group), a carboxyalkyl group (e.g., a Z-carboxyethyl group, a 3-carboxypropyl group, a 2-(2-carboxyethoxy)ethyl group), a p-carboxy aralkyl group (e.g., carboxybenzyl group), a sulfoalkyl group (e.g., a 2-sulfoethyl group, a 3-sulfopropyl group, a 3-sulfobutyl group, a 4- sulfobutyl group, a 2-hydroxy-3-sulfopropyl group, a 2-(3-sulfopropoxy)ethyl group, a 2acetoxy-3- sulfopropyl group, a 3-methoxy-2-(3-sulfopropoxy)- propy] group, a 2-(3-sulfopropoxy)ethoxy ethyl group,

a 2-hydroxy-3-(3'-sulfopropoxy)propyl group, a psulfophenethyl group and a p-sulfonbenzyl group or an aralkyl group (e.g., a benzyl group, a phenylethyl group).

In the above definitions, however, at least one of R, and R must be alkyl group having a sulfo group or an alkyl group having a carboxyl group.

X, represents an anion such as a chloride ion, a bromide ion, an iodide ion, a thiocyanate ion, a sulfate ion, a perchloride ion, a p-toluenesulfonate ion, a methylsulfate ion or an ethylsulfate ion. Finally, n represents 1 or 2, n being 1 when the dye forms an intramolecular salt (betaine-like structure).

The oxacarbocyanine dyes used in this invention are represented by the following general formula (II) sulfamyl group, an alkylaminosulfonyl group (e.g., an wherein 1 2 3, and 4 each p n a y r g n atom, a lower alkyl group preferably having up to 4 carbon atoms (e.g., a methyl group, an ethyl group, an npropyl group), a halogen atom (e.g., a chlorine atom, a bromine atom, a fluorine atom, an iodine atom), an

alkoxyl group (e.g., a methoxy group, an ethoxy group), a hydroxyl group, a phenyl group (including unsubstituted or substituted phenyl groups, e.g., a phenyl group, a p-sulfophenyl group), a carboxyl group, an alkoxycarbonyl group (a methoxycarbonyl group, an ethoxycarbonyl group), a cyano group, a trifluoromethyl group, an amino group (e.g., an amino group, The oxazole ring of the benzimidazolooxacarbocyaan alkylamino group such as a methylamino group, a nine expressed by general formula (I) is a B-naphtooxdimethylamino group), an acyl group (e.g., an acetyl azole ring, an a-naphthooxazole ring or a [Mi-naphgroup), an acyloxyl group (e.g., an acetoxyl group), an thooxazole. The benzene ring in the naphthooxazole alkoxycarbonylamino group (eg, an ethoxycar- 5 ring may be substituted with a substituent as is convenbonylamino group) or a carboalkoxyl group (e.g., a tionally used in cyanine dyes that does not adversely carboethoxy group)wherein any alkyl moiety of B B affect the photographic effect (e.g., sensitivity and B or R preferably has 1-4 carbon atoms. fog).

R,, represents a hydrogen atom, a lower alkyl group Typical examples of benzimidazole.oxacarbocyanine preferably having up to 4 carbon atoms (e.g., a methyl 10 dyes as are used in the present invention are shown group, an ethyl group), or an aryl group (including an below for purposes of illustration, but such examples unsubstituted or substituted aryl group, e.g., a phenyl should not be taken to limit the sensitizing dyes used in group). this invention.

c-cn=ca-ca=c\ 'f/ 01 N (in so i; ii a 2 5 2 5 a 01 N\ +/C-CH:CH-CH=C i C1 Br- I (CH2)2COOH 051 R and R each has the same meaning as R, and R 0 Typical examples of the oxacarbocyanine dye used in in general formula (I), X has the same meaning as X this invention are shown below for purposes of illustraand m has the same meaning as n. tion. However, the sensitizing dyes used in this invention are not limited thereto.

CH SO H CH :011 (hou- (21 The first feature of this invention is that a better supersensitization effect is obtained using a combination of the benzimidazolo.oxacarbocyanine dye represented by general formula (I) and the oxacarbocyanine dye represented by general formula (ll). A markedly high spectral sensitivity is obtained in particular when at least one of the 5-position or the 6-position of the benzimidazolo nucleus in general formula (I) is substituted with a halogen atom and the 5-position of the benzoxazole nucleus in general formula (ll) is substituted with a halogen atom or an alkoxyl group.

The second feature of this invention is that when a combination of the sensitizing dyes of this invention is used, the residual color or dyes based on the sensitizing dyes in the processed photographic elements are lessened. Among conventional sensitizing dyes, sensitizing dyes where all of the nitrogen atoms of the heterocyclic ring have been substituted by lower alkyl groups, such as the comparison dyes A and B shown below, tend to leave a large amount of color stain or residual dyes in the processed photosensitive elements. In particular, when the processing time is short, the extent of color stain or residual dyes is large. On the other hand, because in the sensitizing dye represented by general formula (I) used in this invention at least one of R and R which are the substituent groups of the nitrogen atoms of the heterocyclic ring, is an alkyl group having a sulfo group or an alkyl group having a carboxy group, the amount of color stain or residual dye is extremely low. Further, the sensitizing dye of general formula (II) also gives very low color stain. Accordingly, a combination of both types of sensitizing dyes gives a silver halide photographic emulsion having a very low degree of color stain.

The third feature of this invention is that when the combination of the sensitizing dyes of this invention is used together with anionic compounds which usually degrade the spectral sensitizing action, such as a lightabsorbing dye having a sulfo group in the chemical structure, a gelatin precipitant having a sulfo group, or a coupler for color photographic elements, the combination of dyes of this invention nonetheless imparts a high sensitivity to the silver halide emulsion.

It is generally believed that a sensitizing dye having a nitrogen atom in a heterocyclic ring which is substituted by an alkyl group having a sulfo group or an alkyl group having a carboxy group gives, when present together with a color coupler, a high sensitivity, However, it has been observed that the sensitizing dyes rep resented by general formula (I) or the sensitizing dyes represented by general formula (ll) have almost no spectral sensitizing effect when these sensitizing dyes are used individually with a color coupler. Therefore,

SO H

it is quite astonishing that when a combination of sensitizing dyes represented by the general formula (I) and general formula (ll) is used with a color coupler, a high spectral sensitivity is obtained.

The fourth feature of this invention is that when a combination of the aforesaid sensitizing dyes of this invention is used toogether with a coupler for color photographic elements in a silver halide emulsion the spectral sensitivity of the silver halide emulsion thus sensitized is not substantially reduced during storage of the silver halide emulsion or during storage of photosensitive elements containing such a silver halide emulsion.

The fifth feature of this invention is that by using sensitizing dyes selected from dyes represented by general formulae (1) and (ll) a spectral sensitivity stable to a safe light as is usually employed for processing color positive films and color photographic papers is obtained. Supersensitizing combinations of certain kinds of oxacarbocyanine dyes and certain kinds of benzimidazolocarbocyanine dyes are known, as disclosed in Japanese Pat. Publication No. 2288/1968. The benzimidazolocarbocyanine dye showing the most remarkable supersensitizing effect among the dyes described in the above Japanese Patent has a benzimidazole nucleus substituted at the 5- and 6-positions thereof by a chlorine atom, and the sensitization maximum of the dye is at about 580 mu, although this maximum varies somewhat according to the nature of the silver halide emulsion to be employed. Also, a benzimidazolocarbocyanine dye having a benzimidazole nucleus substituted by a chlorine atom at the 5-position has a sensitization maximum at a longer wave length than 570 mu.

Accordingly, in the case of using the aforesaid benzimidazolocarbocyanine dye in which the 5- and 6- position of the benzimidazole nucleus have been substituted by a chlorine atom or in which the 5-position of the benzimidazole nucleus has been substituted by a chlorine atom in a combination with the oxacarbocyanine dyes described in the above Japanese Patent, such a combination gives severe fog under a safe light as is used for color positive films or color photographic papers, thereby making the use of such a sensitizing combination impractical even when a small amount of the benzimidazolocarbocyanine dye is used, for instance, even when the benzimidazolocarbocyanine dye is used in an amount of one-tenth by weight of the amount of the oxacarbocyanine dye.

On the other hand, the benzimidazole.oxacarbocyanine dye of this invention represented by the general formula (I) in which the 5- and 6-positions have been substituted by a chlorine atom has'its sensitization maximum at about 565 mp. at the longest, and thus a photographic emulsion containing the dyes of this invention can be safely used under a safe light, i.e., it is stable.

The dyes of general formula (I) are described in, e.g., Japanese Patent Publication No. 14030/ 1969 (filed on Jan. 18, 1966), etc., and may be readily synthesized by referring to the descriptions of the above patent or may be synthesized bymethods similar to the methods described in that specification.

The dyes of general formula (11) are described in, e.g., French Pat. No. 1,108,788; U.S. Pat. No. 2,503,776; and British Pat. Nos. 840,223 and 841,119. These sensitizing dyes may be readily synthesized by referring to the descriptions of these patents or may be synthesized by methods similar to those described in the recited patents.

The silver halide used in the photographic emulsion in this invention can be selected from among those commonly used in the photographic arts, for instance, silver chloride, silver bromide, silver iodide, silver chlorobromide, silver iodobromide, or silver chloroiodobromide.

However, the invention is quite advantageously used with a silver halide photographic emulsion containing silver chlorobromide or silver chloroiodobromide. in a silver chlorobromide emulsion, it is particularly advantageous to further add thereto a watersoluble iodide in' an amount of, e.g., 0.005 0.10 mole per mole of AgCl of the silver halide, or a water-soluble bromide in an amount of, e.g., 0.01 0.20 mole per mole of AgCl of the silver halide in the silver halide emulsion after forming the silver halide. Of course, a mixture of a water-soluble bromide and a water-soluble iodide may be added to the emulsion. it is effective to add the water-soluble halide(s) to the emulsion after substantial completion of chemical ripening and especially preferred to add the halide(s) after completion of chemical ripening, followed by the addition of the sensitizing dyes.

in the present invention a gelatino silver halide emulsion is ordinarily used, but other materials known to be equivalents in the art which have no harmful influence on the photosensitive silver halides, for instance, gelatin delivatives such as phthalated gelatin or malonated gelatin, albumin. agar agar, gum arabic, alginic acid, a water-soluble starch such as dextrin, a hydrophilic resin such as polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, or polystyrene sulphonic acid, or cellulose derivatives such as hydroxyethyl cellulose or carboxymethyl cellulose may be used instead of gelatin, or as mixtures thereof.

A supersensitizing amount of the sensitizing dyes of general formula (I) and general formula (ll) may be used in various concentrations thereof, according to the nature of the silver halide emulsion, the concentration of silver halide in the emulsionand the desired effect.

The optimum concentrations of the sensitizing dyes may be determined according to known methods, e.g., by dividing a silver halide emulsion into several portions, incorporating in each portion the sensitizing dyes in different concentration, and measuring the sensitivity of the emulsion. The optimum concentrations of the supersensitizing combination of the dyes in this inven tion can also be easily determined according to the above method.

The sensitizing dyes may be incorporated in a silver halide emulsion by any manner well known in this art dyes may be directly dispersed in a silver halide emulsion or may be incorporated therein as a solution in pyridine, methanol, ethanol, ethanol, methyl cellosolve, acetone or a mixture of such materials, or in water. The organic solvent solution of the sensitizing dyes may, if necessary, be diluted with water. The dissolution of the sensitizing dyes may be conducted using ultrasonic vibrations. Moreover, the methods described in the specifications of Japanese Pat. Nos. 823 1/ 1970, 2389/1969, 27555/1969, and 22948/1969; German Pat. No. 1,947,935; and U.S. Pat. Nos. 3,485,634, 3,342,605, and 2,912,343, can also be used with success.

The sensitizing dyes may be dissolved separately in suitable solvents and the solutions may be separately added to a silver halide emulsion. Alternatively, the sensitizing dyes may be dissolved separately in the same or different solvents and the solutions may be mixed before the incorporation thereof in the silver halide emulsion. it is necessary to uniformly disperse the dyes throughout the silver halide emulsion prior to coating the emulsion containing the sensitizing dyes on a sup port such as a glass sheet, a cellulose derivative film, a polyvinyl resin film (such as a polystyrene film or a polyvinyl chloride film) a polyester film, a synthetic paper, a baryta coated paper, or a polyolefin-coated paper. The sensitizing dyes may be added to the silver halide emulsion at any time during the preparation of the emulsion, but are preferably added after the completion of the second ripening.

The supersensitizing ratio of the sensitizing dye of general formula (I) to the sensitizing dye of general formula (II) is not limited in this invention, but the pre ferred ratio of dye (l) to dye (ii) is in the range of from about 9/1 to about 1/9 by weight, and is varied according to the desired end use. The amounts of the sensitizing dyes used may be changed according to the nature of each silver halide emulsion and the desired effect. In general, optimum sensitivity is obtained by incorporating each sensitizing dye in an amount of from about l X 10' to about 5 X 10 moles per gram mole of silver halide. In general, too small or too great an amount of the dye added decreases or does not increase the sensitivity of the emulsion.

The silver halide photographic emulsion of this invention may also be sensitized by any other well known procedure, i.e., by a noble metal sensitizer (see U.S. Pat. Nos. 2,540,085, 2,597,856, 2,597,915, 2,399,083, etc.), a sulfur sensitizer (see U.S. Pat. Nos. 1,574,944, 2,278,947, 2,440,206, 2,410,689, 3,189,458, 3,415,649, etc.), a reduction sensitizer (see U.S. Pat. Nos. 2,518,698, 2,419,974, etc.,), or an alkyleneoxide sensitizer, or by combinations thereof. The silver halide emulsion may contain, if desired, an antifoggant such as nitrobenzimidazole, or ammonium chloroplatinite a sium chloroaurate, aurousthiosulfate and potassium chloropalladate.

Examples of the reduction sensitizers are tin chloride, phenylpydrazine and reduction.

The color couplers preferably used in this invention are described in the specifications of, e.g., US. Pat.

Nos. 2,600,788 and 2 80l,l7l; British Pat. No. 904,852; Japanese Pat. No. 6031/1965; etc.

The following known couplers are exemplary of those used in this invention in combination with the sensitizing dyes of general formula (I) and (ll):

0 11 0 H2C- C-NHCO Q 0 )3 NHCOCH2O c H f) HN N nhcocn -o C H (t) N micoclzn 0 11 /N=C- o N fi ---cH 50 M 0 /N= C-NHCOCHZCH a n N OOH --cH N= C-NHCO Q N l Minoan-0 m oca coqn CONH QCOCHZCONH-QSOZN COCH2CONH' ocn COCHZCONMQ 111100011 ocit The symbol (t) in the above formulae, where used,

EXAMPLE 1' A solution in methanol of the dyes indicated in Table l was added to a silver iodobromide emulsion (lzBr ratio 6 mol 94 mol prepared by the standard method in the art to form a spectrally sensitized silver iodobromide emulsion (100 g of gelatin and 0.57 mol of Ag per Kg of emulsion). Subsequently, a coupler of the following structural formula was incorporated into the liquid emulsion, and 10 cc per kilogram of the CHZCHZCHZQ c n u) emulsion of a 2% aqueous solution of sodium nonylbenzenesulfonate and 10 cc per kilogram of the emulsion of a 2% aqueous solution of 2,4-dichloro-6- hydroxy-S-triazine were added to the emulsion. The resulting mixture was coated on a cellulose triacetate base film and dried to produce a sample.

The same samples were allowed to stand for 24 hours at 40C in air containing formaldehyde gas in an amount of about 0.1 g per 10 liter of air. The density of fog occurring in the sample at the end of this time was measured in the same manner as above. The results obtained are shown in Table l.

' comparisons, and gave remarkably smaller fog. The efl. Color development 24C ll minutes fect of the present invention is clearly shown in the 2. Rinsing N do seconds above l i; EEK-:51? 33 f 1222:}? While the invention has been described in detail and 5. Bleaching do. 2 minu es 5 with reference to specific embodiments thereof, it will fixing" be apparent to one skilled in the art that various x. ilinsing do. 6 minutes changes and modifications can be made therein with- H9): gaggin hath out departing from the spirit and scope thereof.

- What IS claimed is: 10 l. A silver halide photographic emulsion comprising Dye C used for comparative purposes was anhydroa supersensitizing amount of at least one benl,l-diethyl-3,3'-disulfobutyl-5,5,',6,6'-tetrazimidazolo.oxacarbocyanine dye represented by genchlorobenzimidazolocarbocyanine hydroxide. eral formula (I) H 2? ff NHCO 5 11 C N NHCOCH -o c H (t) 2 5 11 O N C Cl R A 01 A l 5 =CH-CH=CH- (I) N N l A l l and at least one oxacarbocyanine dye represented by general formula (ll) =CH-C=CH (II) N N B l a R L L, 5

wherein A, and A each represents a hydrogen atom, TABLE 1 i V a halogen atom, a hydroxylgroup, an alkoxyl group, an sensitizing dye Relative Fog Maxi- Fog obtained amino group, an acylamido group, an .acyloxyl group, (mglsnver/mol) green i' after exposure an alkoxycarbonylamino group, a cyano group, a triflun. m to f ld h d oromethyi group, an alkoxycarbonyl group, an alkylsulvity (rim) gas for 24 hrs. fonyl group, a sulfamyl group, an .alkylaminosulfonyl (Hum 80 0J3 560 015 group, a morpho lino sulfony] group, a morpholinocar- (lI)-l(85) 100 0.10 555 018 bonyl group, a piperidmosulfonyl group, a carbamoyl (18 -631(98); 126 0.12 22(5)- 0-l8 group, or an alkylcarbamoyl group; (1)409) 85 (H2 560 016 A and A, represent the atomic groups necessary to (062819 126 0.12 550- 0.20 form a benzene ring togetheryB B B and B are sef j i loo 0. 228 (H4 lected from the group consisting of a hydrogen atom, (l)-2(l 132 0.12 550- 0.13 a lower alkyl group, a halogen atom, an alkoxyl group, 32 (125) 85 0 U 232 0 56 a hydroxyl group, a phenyl group, a carboxyl group, an C(20)+ 1 16 0:12 56f 012,0 alkoxycarbonyl group, a cyano group, a trifluoromethyl 575 group, an amino group, an acyl group, an acyloxyl group, an alkoxycarbonylaminogroup or a carbalkoxy The relative green sensitivity was determined assuming gr p; h and 2 each represents an alkyl g p; a! that green sensitivity of an emulsion containing mg least one of R, and R being a sulfoalkyl group or a carof Dye (ll)-l per mol of silver was 100. boxyalkyl group; R,, represents a hydrogen atom, an The combination of dyes according to this invention alkyl group or an aryl group; R and R, have the-same exhibited a larger sensitizing action than those of the meaning as R, and R X, represents an anion; m and n each represents l or 2; said dyes forming an intramolecular salt when m and n are l; and X represents an anion.

2. The silver halide photographic emulsion as set forth in claim 1 wherein the halogen atom is chlorine, bromine, fluorine or iodine; the alkoxy group is methoxy or ethoxy; the amino group is an amino group, methylamino or dimethylamino; the acylamide group is an acctoamide group; the acyloxyl group is an acetoxy group; the carboalkoxy group is an carboethoxy group; the alkoxycarbonyl amino group is an ethoxycarbonyl amino group; the alkoxycarbonyl group is a methoxycarbonyl or ethoxycarbonyl group; the alkylsulfonyl group is'a methylsulfonyl group; the alkylaminosulfonyl group is ethylaminosulfonyl or diethylaminosulfonyl in each of A, or A and wherein the alkyl group is methyl, ethyl group, n-propyl, vinylmethyl, hydroxyalkyl, acetoxyalkyl, alkoxyalkyl, alkyl having a carboxy group, alkyl having a sulfo group or aralkyl in each of R, R, and R or R and R 3. The silver halide photographic emulsion as set forth in claim 2 wherein the hydroxy alkyl group is 2- hydroxyethyl or 4-hydroxybutyl; the acetoxy alkyl group is Z-acetoxyethyl or 3-acetoxypropyl; the alkoxyalkyl group is Z-methoxyethyl or 4-butoxybutyl; the alkyl group having a carboxy group is 2-carboxyethyl, 3-carboxypropyl, 2-(2-carboxyethoxy)ethyl or pcarboxybenzyl; the alkyl group having a sulfo group is Z-sulloethyl, 3-sulfopropyl, 3-sulfobutyl, 4-sulfobutyl, 2-hydroxy-3-sulfopropyl. 2-( 3-sulfopropoxy )ethyl. 2-acctoxy-B-sulfopropyl. 3-methoxy-2-t3-sulfopropoxy)propyl. 2-lZ-sultbpropoxykthoxyl ethyl, Z-hydroxy- 3-(3-sulfopropoxy)propyl, sulfophenethyl or psulfobenzyl; and the aralkyl group is benzyl or phenethyl.

and

l X H) to about 5 X It) moles per gram-mole of silver halide in the emulsion.

7. The silver halide photographic emulsion as set forth in claim 1 wherein the silver halide is silver chlorobromide or silver chlorobromoiodide.

8. The silver halide photographic emulsion as set forth in claim 7 wherein the silver halide is silver chlorobromide.

9. The silver halide photographic emulsion as set forth in claim 8 wherein said silver halide emulsion further contains an iodide in an amount of (LOGS-0.10 mole and/or a bromide in an amount of 0.0l-O.20 mol respectively, per mole of silver chloride constituting the silver halide.

10. The silver halide photographic emulsion as set forth in claim 1 wherein said silver halide photographic emulsion contains a color coupler.

11. The silver halide photographic emulsion as set forth in claim 10 wherein the color coupler is a magenta coupler.

12. The silver halide photographic emulsion as set forth in claim 1 wherein said halide photographic emulsion contains a light absorbing dye.

13. The silver halide photographic emulsion as set forth in claim 1 wherein said benzimidazolo.oxacarbocyanine dye represented by general formula (I) is substituted by a halogen atom in at least one of the 5- or -positions of the benzimidazole nucleus thereof.

14. The silver halide photographic emulsion as set forth in claim I wherein said oxacarbocynnine dye represented by general formula (ll) is substituted by a hailogen atom at the 5-position of the bcnzoxnzolc nucleus thereof.

15. A color photographic light-sensitive element comprising a support having thereon a layer of the silver halide photographic emulsion as set forth in claim 10.

16. The silver halide photographic emulsion as set forth in claim 1 wherein the oxazole ring of the benzimidazolo.oxacarbocyanine represented by general formula (I) is a B-naphthooxazole ring, an a-naphthooxazole ring or a Bfi-napthoxazole ring.

17. A silver halide photographic emulsion containing a supersensitizing amount of the combination selected from the group of 

1. A SILVER HALIDE PHOTOGRAPHIC EMULSION COMPRISING A SUPERSENSITIZING AMOUNT OF AT LEAST ONE BENZIMIDAZOLO.OXACARBOCYANINE DYE REPRESENTED BY GENERAL FORMULA (1)
 2. The silver halide photographic emulsion as set forth in claim 1 wherein the halogen atom is chlorine, bromine, fluorine or iodine; the alkoxy group is methoxy or ethoxy; the amino group is an amino group, methylamino or dimethylamino; the acylamide group is an acetoamide group; the acyloxyl group is an acetoxy group; the carboalkoxy group is an carboethoxy group; the alkoxycarbonyl amino group is an ethoxycarbonyl amino group; the alkoxycarbonyl group is a methoxycarbonyl or ethoxycarbonyl group; the alkylsulfonyl group is a methylsulfonyl group; the alkylaminosulfonyl group is ethylaminosulfonyl or diethylaminosulfonyl in each of A1 or A2; and wherein the alkyl group is methyl, ethyl group, n-propyl, vinylmethyl, hydroxyalkyl, acetoxyalkyl, alkoxyalkyl, alkyl having a carboxy group, alkyl having a sulfo group or aralkyl in each of R, R1 and R2, or R3 and R4.
 3. The silver halide photographic emulsion as set forth in claim 2 wherein the hydroxy alkyl group is 2-hydroxyethyl or 4-hydroxybutyl; the acetoxy alkyl group is 2-acetoxyethyl or 3-acetoxypropyl; the alkoxyalkyl group is 2-methoxyethyl or 4-butoxybutyl; the alkyl group having a carboxy group is 2-carboxyethyl, 3-carboxypropyl, 2-(2-carboxyethoxy)ethyl or p-carboxybenzyl; the alkyl group having a sulfo group is 2-sulfoethyl, 3-sulfopropyl, 3-sulfobutyl, 4-sulfobutyl, 2-hydroxy-3-sulfopropyl, 2-(3-sulfopropoxy)ethyl, 2-acetoxy-3-sulfopropyl, 3-methoxy-2-(3-sulfopropoxy)propyl, 2-(2-sulfopropoxy)ethoxy) ethyl, 2-hydroxy-3-(3-sulfopropoxy)propyl, sulfophenethyl or p-sulfobenzyl; and the aralkyl group is benzyl or phenethyl.
 4. The silver halide photographic emulsion as set forth in claim 1 wherein a binder of the emulsion comprises gelatin.
 5. The silver halide photographic emulsion as set forth in claim 1 wherein the ratio by weight of dye (I) to dye (II) is in the range of from about 9/1 to about 1/9.
 6. The silver halide photographic emulsion as set forth in claim 1 wherein the amount of the sensitizing dye added to the emulsion iS in the range of from about 1 X 10 6 to about 5 X 10 3 moles per gram-mole of silver halide in the emulsion.
 7. The silver halide photographic emulsion as set forth in claim 1 wherein the silver halide is silver chlorobromide or silver chlorobromoiodide.
 8. The silver halide photographic emulsion as set forth in claim 7 wherein the silver halide is silver chlorobromide.
 9. The silver halide photographic emulsion as set forth in claim 8 wherein said silver halide emulsion further contains an iodide in an amount of 0.005-0.10 mole and/or a bromide in an amount of 0.01-0.20 mol respectively, per mole of silver chloride constituting the silver halide.
 10. The silver halide photographic emulsion as set forth in claim 1 wherein said silver halide photographic emulsion contains a color coupler.
 11. The silver halide photographic emulsion as set forth in claim 10 wherein the color coupler is a magenta coupler.
 12. The silver halide photographic emulsion as set forth in claim 1 wherein said halide photographic emulsion contains a light absorbing dye.
 13. The silver halide photographic emulsion as set forth in claim 1 wherein said benzimidazolo.oxacarbocyanine dye represented by general formula (I) is substituted by a halogen atom in at least one of the 5- or 6-positions of the benzimidazole nucleus thereof.
 14. The silver halide photographic emulsion as set forth in claim 1 wherein said oxacarbocyanine dye represented by general formula (II) is substituted by a halogen atom at the 5-position of the benzoxazole nucleus thereof.
 15. A color photographic light-sensitive element comprising a support having thereon a layer of the silver halide photographic emulsion as set forth in claim
 10. 16. The silver halide photographic emulsion as set forth in claim 1 wherein the oxazole ring of the benzimidazolo.oxacarbocyanine represented by general formula (I) is a Beta -naphthooxazole ring, an Alpha -naphthooxazole ring or a Beta , Beta -napthoxazole ring.
 17. A silver halide photographic emulsion containing a supersensitizing amount of the combination selected from the group of 